<p>MIAMI | Miami-Dade Police say a correctional officer was shot and killed in his own driveway, but a motive for the shooting is not yet known.</p><p>Authorities say 46-year-old Andrew Johnson was a 10-year veteran of the Miami-Dade Corrections and Rehabilitation Department. He was found shot and killed Saturday evening.</p><p>Police have not yet many any arrests.</p>